The proposed project will explore, with microelectrode recordings on acute preparations and with simple behavioral tests on normal animals, the relations between the development of receptive field properties in visual structures and the development of visually guided behaviors in the early postnatal period. It is hoped that this project will discover general principles about the changes in neural functioning which mediate the onset and development of visually guided behaviors. Preliminary recordings in the upper layers of the superior colliculus in Pentothal anesthetized, paralyzed kittens 10 to 39 days of age have found that a correlation exists between the development of direction selective responses in superior colliculus cells and the development of visual tracking responses in the kittens. The experiments will be aimed at (1) further study and quantification of the development of tracking and other visual behaviors in kittens; (2) further study and quantification of the development of direction selectivity and other receptive field properties in the superior colliculus of kittens; (3) investigation of whether the correlation is a causal relationship, with the development of direction selective cells responsible for the development of visual tracking; (4) study of the neural mechanisms involved in the development of direction selectivity in the superior colliculus; if time permits, (5) exploration of other structures in the visual system for receptive field changes during visual development which might correlate with the development of other visual behaviors; (6) preliminary exploration of another species, the tree shrew, to investigate whether neural mechanisms underlying visual development in kittens generalize to other species with known differences in visual system anatomy.